Fix case-insensitive boolean deserialization

The visitBoolean() method only accepts lowercase "true"/"false" but XML APIs (notably .NET-based services) commonly return "True"/"False".

Author: NikoGrano

src/XmlDeserializationVisitor.php

@@ -142,7 +142,7 @@ public function visitBoolean($data, array $type): bool
     {
         $this->assertValueCanBeCastToString($data);
 
-        $data = (string) $data;
+        $data = strtolower((string) $data);
 
         if ('true' === $data || '1' === $data) {
             return true;

tests/Serializer/XmlSerializationTest.php

@@ -79,7 +79,16 @@ public function testXMLBooleans($xmlBoolean, $boolean)
 
     public static function getXMLBooleans()
     {
-        return [['true', true], ['false', false], ['1', true], ['0', false]];
+        return [
+            ['true', true],
+            ['false', false],
+            ['1', true],
+            ['0', false],
+            ['True', true],
+            ['False', false],
+            ['TRUE', true],
+            ['FALSE', false],
+        ];
     }
 
     public function testAccessorSetterDeserialization()